No code changes, just catching up with the BOLT changes which rework our
blinded path terminology (for the better!).
Another patch will sweep the rest of our internal names, this tries only to
make things compile and fix up the BOLT quotes.
1. Inside payload: current_blinding_point -> current_path_key
2. Inside update_add_htlc TLV: blinding_point -> blinded_path
3. Inside blinded_path: blinding -> first_path_key
4. Inside onion_message: blinding -> path_key.
5. Inside encrypted_data_tlv: next_blinding_override -> next_path_key_override
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is complicated, and I needed to write it down. All the current routines
are spread through the code, and I wanted it all in one place.
This implementation also support *joining* two paths together, which we
previously didn't.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
